New Member - Frame advice

[Nourish]

I saw recentley a rigid framed B31 and took a fancy to it but I'd rather a low comp twin engine - hence joining this forum. My question(s) is   if I were to find an earlier A7/A10 engine and box(bolt up) would it fit into a singles frame or would I have to use a twins frame? - or how about the rigid subframe - does a singles fit a twins main frame? Thanks for any help.

[muskrat]

G'day Nourish  .
I'm not 100% sure but I don't think so. The twins rigid and spring (plunger) sub frames will swap. Have a look here  http://bsa-a10.hailwood.com/bsaframes.html 
Cheers

[duTch]

 Hiya Nourish,..... Dude I have to be honest from experience, you can do WhatEVER you want to do.... but to make it easy on yourself, we're here to help.

  I found a frame that I figured would make a good ride-and it has, in the end(30 years later)- frikkin awesome in fact, but even though I jammed in the engine that should have been there, and other bits that I thought would work, they weren't quite right enough, and I've ended up with an almost-ish factory ride......
It can be hard work,and unless you have access to lots of bits and tooly stuff, it can be easier to aim for a variation of stock article...,but don't let me deter you

  As I said if yer keen we're here to help. Good luck and cheers, duTch

[Jules]

I thought the singles had a jiggle in the RH downtube that gets in the way for twins?

[Triton Thrasher]

I thought the singles had a jiggle in the RH downtube that gets in the way for twins?

Swinging arm singles' frames have a kink in the timing side bottom tube, to clear the oil pump. That means it is simple(ish) to put an engine and gearbox from a swinging arm twin into a swinging arm single's frame.

Putting a swinging arm single engine into a twin's frame would require a bit of chopping and altering to the bottom tube.

A rigid single has the gearbox on a sliding bottom mount. The gearbox on a rigid twin is bolted to the crankcase.  I don't see an engine swap being an easy drop-in fit.

I'm relying on memory. If anyone knows better, put us right.

[wilko]

 B series rigid frames were open on the bottom but a twin wouldn't fit anyway.
http://s244.photobucket.com/user/takka22/media/001-6.jpg.html

[muskrat]

And Wilko wins 1st prize in the beauty contest.
Cheers

[KiwiGF]

As it happens i have a b31 rigid project on the go, and as per dutchs post anything is possible given time and resources......but the rigid B series single frames are pretty flimsy, with single down tubes and a bolt on rear sub frame, options are to bolt on either rigid or plunger sub frames - i have both for my project but will go for the rigid option assuming i can find a wheel to fit the sub frame.

Are you thinking of putting a twin engine in that type of singles frame?

The rigid a7 is very good looking, i was out riding with a mate yesterday who has one. They are rare and tend to be expensive!

[duTch]

 Hey Nourish, did you see Musky's post for the frame, it's about what you need, except for the aftermarket bends, and shipping.....??
Good luck, duTch

[Tomcat]

Welcome aboard Nourish. The advice given above is good advice, but can i offer something I've learned the hard way? If you like spending your time in the shed, buy basket cases, projects and parts. If you plan to do a bit of riding, buy a complete runner. The early A7 rigid is a wonderful motorcycle to ride and has pleasing lines to look at. Cheers Tomcat

[wilko]

And Wilko wins 1st prize in the beauty contest.
Cheers

I'm not that feral! It's a mate of mine!

[Nourish]

Thank You all for the messages, Looking at the single and twins together they look pretty similiar but looking at the frame drawings (thanks muskrat) then all becomes clear that the frames are so different. I wouldn't want to chop about anything this old.

duTch - your post - "Hey Nourish, did you see Musky's post for the frame, it's about what you need, except for the aftermarket bends, and shipping.....??
Good luck, duTch" 
  -   I cant find it - can you direct me to it?


Cheers

[muskrat]

http://www.a7a10.net/forum/index.php?topic=7506.0
There you go Nourish.
As stated the freight would be a killer.
Cheers

[fido]

The rigid a7 is very good looking, i was out riding with a mate yesterday who has one. They are rare and tend to be expensive!

Things must have changed then. They were always rare but when I bought mine in the '90s the rigids were cheaper than the swinging arm models.